Let's roll up our sleeves and solve this. We have 125 and we're going to multiply it by 131, essentially adding 125 to itself 131 times.
Step 1: 0 + 125 = 125
Step 2: 125 + 125 = 250
Step 3: 250 + 125 = 375
Step 4: 375 + 125 = 500
Step 5: 500 + 125 = 625
Step 6: 625 + 125 = 750
Step 7: 750 + 125 = 875
Step 8: 875 + 125 = 1000
Step 9: 1000 + 125 = 1125
Step 10: 1125 + 125 = 1250
Step 11: 1250 + 125 = 1375
Step 12: 1375 + 125 = 1500
Step 13: 1500 + 125 = 1625
Step 14: 1625 + 125 = 1750
Step 15: 1750 + 125 = 1875
Step 16: 1875 + 125 = 2000
Step 17: 2000 + 125 = 2125
Step 18: 2125 + 125 = 2250
Step 19: 2250 + 125 = 2375
Step 20: 2375 + 125 = 2500
Step 21: 2500 + 125 = 2625
Step 22: 2625 + 125 = 2750
Step 23: 2750 + 125 = 2875
Step 24: 2875 + 125 = 3000
Step 25: 3000 + 125 = 3125
Step 26: 3125 + 125 = 3250
Step 27: 3250 + 125 = 3375
Step 28: 3375 + 125 = 3500
Step 29: 3500 + 125 = 3625
Step 30: 3625 + 125 = 3750
Step 31: 3750 + 125 = 3875
Step 32: 3875 + 125 = 4000
Step 33: 4000 + 125 = 4125
Step 34: 4125 + 125 = 4250
Step 35: 4250 + 125 = 4375
Step 36: 4375 + 125 = 4500
Step 37: 4500 + 125 = 4625
Step 38: 4625 + 125 = 4750
Step 39: 4750 + 125 = 4875
Step 40: 4875 + 125 = 5000
Step 41: 5000 + 125 = 5125
Step 42: 5125 + 125 = 5250
Step 43: 5250 + 125 = 5375
Step 44: 5375 + 125 = 5500
Step 45: 5500 + 125 = 5625
Step 46: 5625 + 125 = 5750
Step 47: 5750 + 125 = 5875
Step 48: 5875 + 125 = 6000
Step 49: 6000 + 125 = 6125
Step 50: 6125 + 125 = 6250
Step 51: 6250 + 125 = 6375
Step 52: 6375 + 125 = 6500
Step 53: 6500 + 125 = 6625
Step 54: 6625 + 125 = 6750
Step 55: 6750 + 125 = 6875
Step 56: 6875 + 125 = 7000
Step 57: 7000 + 125 = 7125
Step 58: 7125 + 125 = 7250
Step 59: 7250 + 125 = 7375
Step 60: 7375 + 125 = 7500
Step 61: 7500 + 125 = 7625
Step 62: 7625 + 125 = 7750
Step 63: 7750 + 125 = 7875
Step 64: 7875 + 125 = 8000
Step 65: 8000 + 125 = 8125
Step 66: 8125 + 125 = 8250
Step 67: 8250 + 125 = 8375
Step 68: 8375 + 125 = 8500
Step 69: 8500 + 125 = 8625
Step 70: 8625 + 125 = 8750
Step 71: 8750 + 125 = 8875
Step 72: 8875 + 125 = 9000
Step 73: 9000 + 125 = 9125
Step 74: 9125 + 125 = 9250
Step 75: 9250 + 125 = 9375
Step 76: 9375 + 125 = 9500
Step 77: 9500 + 125 = 9625
Step 78: 9625 + 125 = 9750
Step 79: 9750 + 125 = 9875
Step 80: 9875 + 125 = 10000
Step 81: 10000 + 125 = 10125
Step 82: 10125 + 125 = 10250
Step 83: 10250 + 125 = 10375
Step 84: 10375 + 125 = 10500
Step 85: 10500 + 125 = 10625
Step 86: 10625 + 125 = 10750
Step 87: 10750 + 125 = 10875
Step 88: 10875 + 125 = 11000
Step 89: 11000 + 125 = 11125
Step 90: 11125 + 125 = 11250
Step 91: 11250 + 125 = 11375
Step 92: 11375 + 125 = 11500
Step 93: 11500 + 125 = 11625
Step 94: 11625 + 125 = 11750
Step 95: 11750 + 125 = 11875
Step 96: 11875 + 125 = 12000
Step 97: 12000 + 125 = 12125
Step 98: 12125 + 125 = 12250
Step 99: 12250 + 125 = 12375
Step 100: 12375 + 125 = 12500
Step 101: 12500 + 125 = 12625
Step 102: 12625 + 125 = 12750
Step 103: 12750 + 125 = 12875
Step 104: 12875 + 125 = 13000
Step 105: 13000 + 125 = 13125
Step 106: 13125 + 125 = 13250
Step 107: 13250 + 125 = 13375
Step 108: 13375 + 125 = 13500
Step 109: 13500 + 125 = 13625
Step 110: 13625 + 125 = 13750
Step 111: 13750 + 125 = 13875
Step 112: 13875 + 125 = 14000
Step 113: 14000 + 125 = 14125
Step 114: 14125 + 125 = 14250
Step 115: 14250 + 125 = 14375
Step 116: 14375 + 125 = 14500
Step 117: 14500 + 125 = 14625
Step 118: 14625 + 125 = 14750
Step 119: 14750 + 125 = 14875
Step 120: 14875 + 125 = 15000
Step 121: 15000 + 125 = 15125
Step 122: 15125 + 125 = 15250
Step 123: 15250 + 125 = 15375
Step 124: 15375 + 125 = 15500
Step 125: 15500 + 125 = 15625
Step 126: 15625 + 125 = 15750
Step 127: 15750 + 125 = 15875
Step 128: 15875 + 125 = 16000
Step 129: 16000 + 125 = 16125
Step 130: 16125 + 125 = 16250
Step 131: 16250 + 125 = 16375

So, 125*131 = 16375